Extraction Process Optimization,Structure Characteristics And Antioxidant Activity Of Collagen From Muscle Of Sea Slug Onchidium Struma

Onchidium struma is a kind of important subtropical mollusks which has high nutrition and medical value,belonging to gastropoda.It usually appears in the reed grass of high tide of interrtidal zone,fed with the organic matter and single cell algae in the mudflats.It has been reported that O.struma has extremely high nutritional value,including varieties of essential amino acids,which conform to the evaluation standard for protein essential amino acid.Furthermore,it also has a high containing of trace elements such as calcium,phosphorus,iron,zinc and copper.In a word,O.struma is a kind of high-protein and low-fat food,and also has high edible value and health care function,which make it the best choice for losing weight.Some people living in coastal areas usually treat diseases such as asthma,athlete’s foot and indigestion with O.struma,thus,as a kind of tonic as well as rare sea food,it is very popular among people.At present,researches about O.struma in our country are mainly in the fields of system classification,ecological breeding,neurophysiology,embryonic development,nutrition composition analysis,etc,and active materials research is focused on polysaccharide and proteins.However,muscle collagen of O.struma has not yet been researched about.Therefore,to make good use of O.struma,in combination with the previous study about O.struma,the present study used pepsin enzymatic hydrolysis,basing on the raw material of muscle of O.struma,to extract collagen under acidic conditions,and also used orthgonal experiment,to determine the best extracting process of collagen on O.struma.SDS-PAGE、infrared scanning,amino acid composition analysis and other methods were used to analyze the amino acid composition and structure characteristics of collagen from the muscel of O.struma comprehensively.The antioxidant activity of collagen from the muscle of O.struma was analyzed by its DPPH free radical and hydroxyl free radical scavenging ability and Fe²⁺chelating ability.It provided data support for the development of collagen as a new source,and also laied the foundation for the further development and utilization of the active material of O.struma,in order to further prove the folklore’s health care function.The main results are as follow:1、Measured by Hydroxyproline（alkaline water treatment）kit,muscle collagen contenting in O.struma is about 39.01%.The effects of different enzymatic hydrolysis temperature,enzyme addition amounts,and enzymolysis time on collagen extraction were analyzed by single-factor tests to determine the best experiment conditions above.The results show that when the enzymatic hydrolysis temperature,the enzyme addition amounts,and enzymolysis time are 25℃,4mg/ml,and 24h,the collagen extraction rate is the highest.Based on the experiments above,we used orthgonal experiment to determine the conditions when the extraction rate reaches the highest,and the results show that it’s when the temperature,enzyme addition amounts,and enzymolysis time are35℃,8mg/ml,and 24h,the extraction rate is the highest,which reaches to 73.09%.2、Muscle collagen contenting in O.struma consists of 3 polypeptide chains（α₁、α₂、α₃）analyzed by SDS-PAGE.The result of gel electrophoresis shows that the molecular weight ofα₁.α₂.α₃ chains are about 100KDa,70KDa and 40⁵0KDa,respectively.The obtained collagen has high purity,which is consistent with the result of electrophoresis of type I collagen gel.The infrared scanning spectrum showed that the characteristic absorption peaks of muscle collagen in O.struma were amide I band,amide II band,and amide III band,and the wave numbers were 1659,1549,1237,and 1452 cm^-1,respectively,indicating that there was a complete triple-helical structure and it can protect,isolate,support the tissues and organs.According to the analysis of amino acid composition,the content of Glycine（Gly）was the highest,followed by the characteristic amino acid hydroxyproline（Pro）,the content of cysteine（Met）and lysine（Lys）is relatively low,there is no histidine（His）,and the amino acid composition of collagen is similar.3、The study evaluated the antioxidative activity of muscle collagen in O.struma by using DPPH free radical scavenging ability,hydroxyl radical scavenging ability and ferrous ion sequestration as indicators.The results showed that the hydroxyl radical scavenging ability was the strongest,reaching 83.97%;the DPPH radical scavenging ability was slightly lower than the hydroxyl radical scavenging ability,which was 81.56%;Fe²⁺chelating ability is much weaker,which was only 51.55%.The results demonstrated that the muscle collagen in O.struma has a strong antioxidant activity.